1. Field of the Invention
The present invention relates generally to a wireless power transmitter, a wireless power receiver, and methods of controlling the same, and more particularly, to a wireless power transmitter and a wireless power receiver which can communicate in a predetermined scheme, a method of controlling the wireless power transmitter, and a method of controlling the wireless power receiver.
2. Description of the Related Art
In view of their nature, mobile terminals, such as portable phones and Personal Digital Assistants (PDAs), are powered by rechargeable batteries. To charge the batteries, the mobile terminals supply electric energy to the batteries through additional chargers. Typically, the charger and the battery each have an exterior contact terminal and thus are electrically connected to each other through their contact terminals.
This contact-based charging scheme faces the problem of vulnerability of contact terminals to contamination of rogue devices and to moisture exposure, and the resulting unreliable battery charging due to the outward protrusion of the contact terminals.
To address the above problems, wireless charging or contactless charging technologies have recently been developed and applied to many different electronic devices.
A wireless charging technology is based on wireless power transmission and reception. For example, a portable phone battery is automatically charged when placed on a charging pad, without being connected to an additional charging connector. The use of the wireless charging technology is well known in a wireless electric toothbrush or a wireless electric shaver. The wireless charging technology improves a waterproof function since it wirelessly charges the electronic devices, and improves the portability of the electronic devices because it does not require a wired charger. It is expected that the development of technologies related to the wireless charging technology will be significantly furthered in the coming age of electric cars.
The three wireless charging schemes generally are electromagnetic induction using coils, resonance-based, and Radio Frequency (RF)-microwave radiation based on conversion of electric energy to microwaves.
The electromagnetic induction-based wireless charging scheme has been the most popular, to this point. However, considering recent successful experiments in wireless power transmission over microwaves at a distance of tens of meters in Korea and other overseas countries, it is foreseeable that every electronic product will be charged cordlessly at any time in any place in the near future.
Electromagnetic induction-based power transmission means power transfer between primary and secondary coils. Current is induced when a magnet moves through a coil. Based on this principle, a transmitter creates a magnetic field and a receiver produces energy by current induced by a change in the magnetic field. This phenomenon is known as magnetic induction, and power transmission based on magnetic induction is highly efficient in energy transfer.
Regarding resonance-based wireless charging, in 2005, a system that enables wireless energy transfer from a charger at a distance of a few meters based on the resonance-based power transmission principle by the Coupled Mode Theory was disclosed. This wireless charging system employs the physics concept of resonance, by which when a tuning fork oscillates at a particular frequency, a wine glass next to the tuning fork will oscillate at the same frequency. An electromagnetic wave containing electrical energy was caused to resonate instead of causing sound to resonate. The resonant electric energy is directly transferred only in the presence of a device having the same resonant frequency, while the unused electric energy is reabsorbed into the electromagnetic field rather than being dispersed into the atmosphere. Thus, the resonant electric energy does not affect nearby machines or human bodies, compared to other electronic waves.
Wireless charging is a recent active research area. However, there are no specified standards of wireless charging priority, detection of a wireless power transmitter/receiver, communication frequency selection between a wireless power transmitter and a wireless power receiver, wireless power control, selection of a matching circuit, and allocation of a communication time to each wireless power receiver in a single charging cycle.
Accordingly, there exists a need for developing standards regarding a method of detecting rogue devices on a wireless power transmitter by the wireless power transmitter and a configuration of transmitting related information in a wireless power receiver.